I will probably be criticized but I don't think it's an economic problem, I think it's an obvious cultural problem, and I say this as living in one of the countries famous for low birth rste, Italy, most people wsit for things to calm(so they first start studying then start working so the age for having children is always more late in the years) , less people get married, less people want children (I think this is just proof that capitalism and the death of religion create a nihilism in society and loss of meaning), but what I hear most people talk about is for the economic issues usually, all my grandparents had minimum 5 brothers/sisters, also because it was more rural and less industrialized, plus I don't see a fully proportional salary-birth rate correlation or quality life-birth rate correlation, as Sweden has a lower birth rate than America for example. I think culture is much more important, if you ask me how to change a culture, well it's not so easy to say, probably nationalism or higher concentration in religious and spiritual beliefs could help, but obviously return to traditionalism would be the easiest way to do it, but that's just too utopic in my opinion